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Nervous/Endocrine Systems
Function of the Nervous System
• Coordinates organ system activities to help maintain
homeostasis.
– Homeostasis is the body’s ability to maintain a stable
environment while changes to the external environment take
place.
• Nervous system is the most complex organ system.
• Works closely with the endocrine system to maintain
homeostasis.
– Nervous system controls the body with short, fast, electrical
impulses.
– Endocrine system controls the body with long, slow, chemical
impulses (hormones).
Nervous System Divisions
• The nervous system is divided into two functional
divisions.
– Central Nervous System (CNS): Brain and Spinal Cord
• Brain: where intelligence, memory, and emotion come from.
• Spinal Cord: Integrates and coordinates the processing of
sensory data and the transmission of motor control
(movement).
– Peripheral Nervous System (PNS): Nervous tissue
outside the CNS…10 million in the body.
• Controls the function of muscles and glands.
Peripheral Nervous System
• Somatic nervous system
– Overall control of skeletal muscles.
• Autonomic nervous system
– Provides automatic involuntary regulation of smooth muscle
(digestive system), cardiac
muscle (heart), and glands.
– Divided further into:
• Sympathetic – under stressful
conditions
• Parasympathetic - normal dayto-day activities
Overview of the Nervous System
An Introduction to the Nervous System
• The nervous system sends electrical signals through special
nervous tissue.
• Each nerve cell is also called a neuron: a cell that send and
receive signals.
• The Structure of Neurons
– Dendrites: hair like structures that receive nerve impulses.
– Cell body: where organelles are found.
– Axon: hair like structures that send nerve impulse to other
neurons.
Neurons
Neurons
• Nerve signals travel through neurons as electrical
impulses, but when they reach the end (axon) of the
nerve cell the signal is released as a chemical.
– This chemical signal is called a neurotransmitter.
– The chemical signal is released into the space between
adjacent nerve cells.
– Synapse: the structure/open space that allows for nerve
cells to pass impulse to one another.
Reflex
• A reflex occurs when the body reacts to a stimulus
without thinking about it.
• During a reflex the nerve signal goes to the spinal
cord and right back out to the body to cause a
reaction.
– This is because we need/want to react quickly to
decrease injury.
– Animation
Disorders
• Paralysis occurs when a injury occurs to the spinal
cord that does not allow information from the brain
to be transmitted to muscles.
Part 2
ENDOCRINE SYSTEM
Function of Endocrine System
• The endocrine system controls long-term homeostasis,
such as growth and development.
• It controls the body via chemical impulses called hormones.
• These hormones are released from specialized organs
called glands.
– Each gland releases one type of hormone, and those
hormones travel through the blood to the designated
target cell or organ.
– These hormones then control the functioning of that
target cell or organ.
Hormones
• Hormone control everything in our body:
– Growth
– Development
– Reproduction
– Cell metabolism
– Blood sugar levels
– Stress levels (both short-term and long-term)
– Sleep cycle
– Blood calcium levels and bone strength
Mechanism
• Most hormones are under control by a process called
Negative Feedback.
– Negative Feedback:
• release of a hormone causes a change that suppresses
further release of that hormone
• when hormone levels get too low in the blood the body
stimulates the designated gland to make and release the
hormone until the levels reach homeostasis again.
– For example: in males if testosterone levels get too low
in the blood, the brain signals the testes to make and
release testosterone into the bloodstream, when the
levels get back to normal the testes stop making and
releasing the hormone.
Mechanism
• Some hormones are under Positive Control (though this is
rare).
– Positive Feedback: occurs when the release of a
hormone, causes more hormone to be released
increasing the stimulus.
– For example: when a female is in labor, the hormones
that control her labor increase as she moves through the
labor process, making the uterine contractions stronger
to deliver the baby.
Diabetes
• One major type of endocrine disease that can occur is diabetes.
– Diabetes: occurs when the body cannot control its blood
sugar levels.
• When our blood sugar levels are high, our pancreas releases
insulin (a hormone) to tell our body cells to take sugar inside
their cell membrane to store, this decreases the amount of
sugar in our blood.
– Type 1 diabetes occurs when a person’s pancreas does not make
enough insulin.
– Type 2 diabetes occurs when a person’s body cells does not react to
insulin.